Re: Telegraph C&S Alpine west side

The wire in question is a ground wire.

Such wires were installed on telegraph poles at intervals to bleed off current escape during wet weather when the insulation resistance
of the line was lowered due to moisture providing a leakage path to earth over the wet insulators and via the crossarm and pole.

Without the ground wires at every few poles, this leakage would sometimes get bad enough that current from one telegraph wire would leak over onto adjacent wires on the line
and cause what was termed a "weather cross", (a high resistance short circuit) and made the affected wires work poorly due to current from one wire bleeding over to other wires across the wet path from insulator to insulator via the wet crossarm between them.

The ground wire stapled along the crossarm and down the pole to a spiral on the butt end of the pole deep in the ground would tend to equalize this leakage from all wires to earth on the line and helped prevent leakage from one wire on the line bothering service on the other wires in wet weather by providing an easier common path to earth for the leakage that always occurred....

These ground wires also helped bleed off large static charges from lightning strikes near the line.

A direct lightning strike on the line would usually burn any copper wires down mid-span at the point of strike,
but the larger iron wires (even if burned down) generally conducted the lightning pulse to the nearest pole with a ground or guy wire attached and shredded the crossarm and pole alike as it went to earth.......or started a fire in a nearby depot switchboard.. The ground wires on poles adjacent to depots a few spans in each direction helped mitigate this problem.
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Ed



Edited 1 time(s). Last edit at 09/07/2017 10:56PM by Etrump.